Even with perfect foresight, one’s answer to that question would have to be “No”, but – much more often than not – one is working in the dark.

The great General Ismay, Churchill’s wartime representative on the Chiefs of Staff Committee, summed up the dilemma of peacetime Defence planning: “It is easy to criticise peaceful democracies for their habitual lack of preparedness when a war breaks out, but it is only fair to recognise that the dice are loaded against them. Dictators, bent on aggression are masters of their own timetable. They are free to decide when to strike, where to strike, and how to strike, and to arrange their armament programmes accordingly. Their potential victims, the democracies, with their inherent hatred of war do not know when or where the blow will fall or what manner of blow it will be.”

Ismay was writing in 1960, having recently retired as NATO’s first Secretary-General in the depths of the Cold War era. Then, at least, we knew the identity of our main potential enemies. The situation is far more complex today.

In the Cold War, we faced a powerful State actor, the USSR, fuelled by a ruthless and pervasive ideology. A decade after Communist totalitarianism collapsed in Russia, Islamist totalitarianism took centre stage in the heart of America. By 2001, however, the United Kingdom had drastically reduced the proportion of GDP spent on defence. From six per cent in the 1960s and five per cent in the 1980s, we had come down to three per cent in the mid-1990s, after taking the so-called “peace dividend”.

That was understandable, but then the rot really set in. During the Blair decade, the cost of operations (normally met from Treasury Reserve funds) began to be included in overall defence calculations. That enabled Mr Blair to claim that defence spending had remained roughly constant during his tenure, at 2.5 per cent, but only while heavy involvement in Iraq and Afghanistan persisted. The true figure was nearer 2.1 per cent; and, under Mr Blair’s successors, it would have fallen below the NATO two per cent minimum guideline – without some (technically permissible) creative accountancy during the later Cameron years.

Even with Russia quiescent early in the new century, top military commanders like General Sir David Richards were warning that inadequate defence funding would force us to choose between waging counter-insurgency campaigns, as at present, and continuing to prepare for possible State-versus-State conflict at some unspecified future date. With an emboldened Russia returning to adventurism – in the “near abroad” and in the Middle East – that unacceptable choice became increasingly stark.

We now face potential threats from a powerful state without a totalitarian creed, and from a totalitarian creed without a powerful state. Whether Russian nationalism or Islamist extremism is regarded as the more menacing, the fact remains that it is impossible to insure and prepare against both on the basis of barely two per cent of GDP. Sleight of hand – such as the endless calls for “efficiency savings” – cannot compensate for the losses in capability and capacity inflicted by successive Governments. Wherever one turns in defence, financial black holes loom large.

We are told that the conclusions of the 2015 Strategic Defence and Security Review remain the basis for our policy; but this has left us with a £20 billion shortfall in the Defence Equipment Plan over the next ten years. The Army is struggling to recruit even to a drastically reduced target strength. And now we learn that “new and intensified threats”, principally in cyber-space and in missile technology, require a “National Security Capability Review” to be carried out – with the imminent loss of our Amphibious Assault Ships widely touted to generate the necessary funds. Yet, only last year, I was assured in writing by the Defence Procurement Minister that they would continue in service until 2033 and 2034. The Defence Committee’s devastating report on the “militarily illiterate” proposal to delete those vessels rightly received huge media coverage this February.
When distorted priorities put HS2 above national security, it is time for the new Defence Secretary to take on the Treasury with no holds barred. A lot will depend on the outcome of that battle.